This application includes a microfiche appendix including 2 microfiche and 140 frames.
A portion of the disclosure of this patent document contains material which is subject to a claim of copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all other rights whatsoever.
This invention relates to a control system for controlling the working depth of a tractor-coupled implement as a function of various sensed and operator-controlled parameters.
Various hitch control systems have been designed and built or proposed. Conventional production hydromechanical hitch control systems, such as described in U.S. Pat. No. 3,757,868, have relatively simple controls with which operators have become familiar over a period of years - a console or command lever and a "mix" control. However, by their very nature, the function of such systems has been and is limited in certain respects. For example, if such a system is operating in a draft force responsive mode in a steady state, equilibrium condition, changes in the "load/depth" or "mix" setting will cause significant changes in implement operating depth. If the operator desires to continue operating at the original depth, the operator must make an additional adjustment of the command lever. Also, such a system must vigorously respond to changes in sensed draft force in order to raise and lower an implement through the resistance of the earth in which it operates. This requires a control system with a relatively high gain. However, when such a control system is operated to raise or lower a hitch when the implement is above the ground, this high gain or sensitivity may cause rapid and abrupt hitch movement with resultant undesirable vibration and stress on the linkages and hydraulic components. Furthermore, with the conventional hydromechanical system, when the "mix" control is adjusted to increase the sensitivity of the control system to changes in sensed draft force, the overall gain of the system will be decreased. Also, "mix" control can be moved to adjust this sensitivity beyond a range which is actually useful during field operation.
Various attempts have been made to improve hitch control system performance utilizing electronics and/or microprocessors. See, for example, U.S. Pat. Nos. 4,508,176; 4,518,044 and 4,503,916. However, such systems utilizing electronics have not generally been fully utilized due to factors such as complexity of the operator controls. It would be desirable to provide a hitch control system which has operator controls which are similar to those utilized in the conventional hydromechanical systems, but which has performance advantages made possible by electronics.